A zoom lens device which is a lens device capable of obtaining different focal lengths alone has been used in optical products such as cameras and projectors. In such a zoom lens device, as disclosed in JP-A-2003-202479, a plurality of lens groups is mounted in a mirror barrel, and the lens groups are moved in directions along the optical axis to vary the magnification and to perform focusing.
Each of the lens groups includes at least one lens and an annular lens supporting frame for supporting the lens. For example, three cam followers in the form of pins are radially erected on the outer circumference of the lens supporting frame such that they define equal angles. The mirror barrel includes a zoom cam cylinder formed with a plurality of curved cam grooves into which the cam followers on the lens supporting frame are inserted and a fixed cylinder formed with a plurality of straight cam grooves extending along the optical axis. The cam followers are pushed into the curved cam grooves as a result of a rotation of the zoom cam cylinder to move each of the lens groups along the straight cam grooves in a direction along the optical axis.
In order to obtain high image quality with a zoom lens device, the inclination of each lens group with reference to the optical axis must be small. In the case of the zoom lens device disclosed in JP-A-2003-202479, eccentric rollers are attached to the three cam followers, and the eccentric rollers are rotated with the lens supporting frame mounted in the zoom cam cylinder and the fixed cylinder to change the state of abutment between the cam grooves and the cam followers, thereby adjusting the inclination of each lens group with reference to the optical axis.
However, according to the adjusting method utilizing eccentric rollers disclosed in JP-A-2003-202479, it is difficult to manage and control the direction and amount of a movement of apart of the lens supporting frame that is caused by a rotation of any of eccentric rollers associated with the three cam followers, and such an operation has been time-consuming and has therefore resulted in a cost increase.